A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow that is expanded through the turbine section to drive the compressor section and the fan section. The compressor section typically includes low and high pressure compressors, and the turbine section includes low and high pressure turbines.
A speed reduction device, such as an epicyclical gear assembly, can be utilized to drive the fan section. The speed reduction device permits the fan section to rotate at a speed different than the turbine section, which can increase the overall propulsive efficiency of the engine. In such engine architectures, a shaft driven by one of the turbine sections provides an input to the epicyclical gear assembly that drives the fan section at a reduced speed such that both the turbine section and the fan section can rotate at closer to optimal speeds.
The epicyclical gear assembly requires lubrication to prevent premature wear of bearing surfaces. A primary lubrication subsystem that includes a main pump and main reservoir can provide lubrication to the bearing surfaces during engine operation. An auxiliary lubrication subsystem can utilize lubricant drained from the gear assembly to maintain lubricant flow to the bearing surfaces. The auxiliary lubrication subsystem is typically used when the primary lubrication subsystem is not able to provide sufficient lubricant to the bearing surfaces.
The primary lubrication subsystem may not be able to provide sufficient lubricant to the bearing surfaces when the engine is not operating, or is operating at a relatively low speed. The bearing surfaces can still require lubrication in this situations due to, for example, airflow through the fan section causing the gear assembly to rotate. Also, certain maneuvers with the engine operating may briefly interrupt the operation of the primary lubrication subsystem.